1422

1422 IET | Alldatasheet

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• Manufacturer or author: BS
• PDF pages: 2

Technical content

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1422 Series Page 1 of 2

1422 Datasheet August , 2019

The 1422 is a stable and precise variable air capacitor intended for use as a conƟ nuously adjustable standard of capacitance. One of the most important applicaƟ ons is an AC bridge measurements, either as a built-in standard for subsƟ tuƟ on measurements. It is available in a variety of ranges, terminal confi gu- raƟ ons, and scale arrangements to permit selecƟ on of precisely the required characterisƟ cs. Features:

• A laboratory standard
• For calibraƟ ng working standards
• Working standard
• Capacitance measurement funcƟ ons
• For subsƟ tuƟ on measurements
• For calibraƟ ng instrumentaƟ on Model 1422-D Precision Capacitor Two-terminal - The 1422-D is a dual- range 115 pF and 1150 pF, two-terminal capacitor, direct reading in total ca- pacitance at either range terminal to ground. Three-terminal - The 1422-CB, 1422- CL and 1422-CD are three-terminal capacitors with shielded coaxial termi- nals for use in three-terminal measure- ments. Connection is made via GR- 874 connectors. The calibrated direct capacitance is independent of terminal capacitance to ground, and losses are very low. The 1422-CL has particularly low, constant terminal capacitance, making it suitable for measurement circuits in which high capacitance to guard cannot be tolerated. The 1422-CD is a dual-range 1.1 pF and 11 pF, three-terminal capacitor with direct reading in total capacitance at either range terminal to low. Construction - The capacitor assembly is mounted in a cast frame for rigidity. This frame and other critical parts are made of aluminum alloy selected to give the strength of brass with the lightness of aluminum. The plates of most models are also aluminum, so that all parts have the same temperature coeffi cient of linear expansion. A worm drive is used to obtain high precision of setting. To avoid eccentric- ity, the shaft and the worm are ac- curately machined as one piece. The worm and worm wheel are also lapped into each other to improve smoothness. The dial end of the worm shaft runs n a self-aligning ball bearing, while the other end is supported by an adjustable spring mounting, which gives positive longitudinal anchoring to the worm shaft through the use of a pair sealed, self-lubricating, preloaded ball bearings. Similar pairs of preloaded ball bearings provide positive and invariant axial loca- tion for the main or rotor shaft. Electri- cal connection to the rotor is made by means of a silver-alloy brush bearing on a silver-overlay drum to assure a low- noise electrical contact. Stator insulation in all models is a cross-linked thermosetting modifi ed polystyrene having low dielectric losses and very high insulation resistance. Rotor insulation, where used (Types 1422-CB and -CL), in grade L-4 ste- atite, silicone treated. Accuracy - The errors tabulated in the specifi cations are possible errors, i.e., the sum of error contributions from set- ting, adjustment, calibration, interpola- tion, and standards. When the capacitor is in its normal position with the panel horizontal, the actual errors are almost always smaller. The accuracy is im- proved when the readings are corrected using the 12 calibrated values of ca- pacitance given on the correction chart on the capacitor panel and interpolating linearly between calibrated points. Even better accuracy can be obtained from a precision calibration of approximately 100 points on the capacitor dial, which permits correction for sight residual eccentricities of the worm drive and requires interpolation over only short intervals. This precision calibration is available for the 1422-CL model.
• Stability: beƩ er than 0.02% full scale per year
• SeƩ leable to 40 ppm
• Low temperature coe ffi cient, low losses
• Wide selec Ɵ on to suit needs
• 3 di ff erent models Model 1422-CB/CL/CC Precision Capaci- tor Model 1422-CD Precision Capacitor

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1422 Series Page 2 of 2

ORDERING INFORMATION

1422 Precision Capacitors

Capacitance Range (Min/Max) 100/1150 pF 35/115 pF 50/1100 pF 10/110 pF 5/110 pF 0.5/11 pF 0.05/1.1 pF Initial Accuracy: Picofarads Direct-Reading (Adjustment): Total Capacitance ±1.5* ±0.3* With Corrections from Calibration Chart (supplied) Total Capacitance 0.04 0.04 ±0.01 ±0.002 With Corrections from Precision Calibration (extra charge) Total Capacitance 0.01 0.01 Residuals (typical values): Series Inductance, μH Series Resistance, at 1 MHz 0.06 0.10 0.04 0.05 0.14 0.1 0.13 0.1 0.17 0.17 0.17 Terminal Capacitance, pF, typical high terminal to case low terminal to case min/max scale min/max scale min/max scale min/max scale * Total capacitance is the capacitance added when the capacitor is plugged into a 777-Q3 Adapter Catalog No: Item Name Calibration 1422-9704 1422-D Precision Capacitor 12 points 1422-9916 1422-CB Precision Capacitor 12 points 1422-9809 1422-CC Precision Capacitor 12 points 1422-CD Precision Capacitor 12 points 1422-9508 1422-CLP Precision Capacitor ~100 Stability: Capacitance change with time < 1 scale division (0.02% of full scale) per year Long-term accuracy can be estimated from the stability and the initial accuracy. Calibration: Measured values (supplied) are obtained by comparison at 1 kHz, with working standards whose absolute values are known to and accuracy of ± (0.01% + 0.0001 pF). Each comparison is made to a precision better than ±0.01%. The values of the working standards are determined and maintained in terms of reference standards periodically calibrated by an SI. The indicated value of total capacitance of a two- terminal capacitor is the capacitance added when

1422 Capacitor is plugged into a 777-Q3 Adapter

*. The uncertainty of this method to connection is approximate ± 0.03 pF. * Gilbert Engineering Part Number 0777-9703. Resolution: Dial can be read and set to 1/5 of a small division, i.e. to 0.004% of full scale. BACKLASH: Negligible for any setting reached consistently from lower scale readings; <0.004% of full scale, for settings reached from alternate directions. Temperature Coeffi cient: Approximately +20 ppm/°C, for small temperature changes. Residual Parameters: See table above. Series resistance varies as −fƒ for ƒ > 100 kHz; negli- gible, for ƒ < 100 kHz. Frequency Characteristic: 2-terminal model, see Figure 1. 3-terminal models: 20 and 40 MHz (ap- -CL (each section), respectively. conditions (23°C, RH < 50%). tor terminal connected to panel and shield. Mechanical: Lab-bench cabinet.